1. Field of the Invention
The invention relates to a method of display map data on a personal navigation device, and more particularly, to a method and related device for adjusting a level of map detail shown on the personal navigation device according to a current speed of the personal navigation device.
2. Description of the Prior Art
Global Positioning System (GPS) based navigation devices are well known and are widely employed as in-car navigation devices. Common functions of a navigation device include providing a map database for generating navigation instructions that are then shown on a display of the navigation device. These navigation devices are often mounted on or in the dashboard of a vehicle using a suction mount or other mounting means.
The term “navigation device” refers to a device that enables a user to navigate to a pre-defined destination. The device may have an internal system for receiving location data, such as a GPS receiver, or may merely be connectable to a receiver that can receive location data. The device may compute a route itself, or communicate with a remote server that computes the route and provides navigation information to the device, or a hybrid device in which the device itself and a remote server both play a role in the route computation process. Personal GPS navigation devices are not permanently integrated into a vehicle but instead are devices that can readily be mounted in or otherwise used inside a vehicle. Generally (but not necessarily), they are fully self-contained—i.e. include an internal GPS antenna, navigation software and maps and can hence plot and display a route to be taken.
Personal navigation devices typically provide two-dimensional maps for helping users to navigate to a destination. However, three-dimensional (3D) maps are useful in certain situations as well. For instance, when a pedestrian is holding a personal navigation device, a 3D map showing realistic views of buildings is useful for helping the pedestrian find his way around a city since he can use the buildings as landmarks for helping to navigate. When driving in a car, however, 3D maps can obscure the map view by covering up the upcoming roads and points of interest. In this case, two-dimensional (2D) maps are usually preferred over 3D maps.
Therefore, there is a need for a convenient way of switching between different types of maps, such as 2D and 3D maps depending on how the personal navigation device is being used.